1. Field of the Invention
The present invention relates to the field of so-called dual-mode chip-cards or smart cards, that is, cards which are likely to establish a communication with a read/write terminal via physical contacts as well as via an inductive coupling through an antenna.
2. Description of the Related Art
U.S. Pat. No. 6,168,083 depicts a dual-mode smart card, capable of operating either in a contact mode, or in a contactless mode. This patent provides selecting a communication session of contactless type if an A.C. voltage is induced in the antenna and a session of operation via physical contacts with a read/write terminal in the absence of such an A.C. voltage and if a D.C. voltage is present on the physical contacts provided for this purpose. The smart card is provided with two interfaces, respectively for the contactless mode and the contact mode, with a card memory, as well as with circuits for selecting one of the interfaces. In fact, the circuits of the smart card are activated as soon as a sufficient supply voltage level is detected by a level detection circuit, and the contactless interface is selected if another detector detects the present of an A.C. voltage across the antenna.
A disadvantage of the system provided by this document is that it does not allow switching from a contact operation to a contactless operation during a same operating session, that is, when the selection circuit has selected one of the interfaces. A system reset must then be awaited to, if desired, allow a switching by a new detection phase.
Another disadvantage of the system described by the above-mentioned document is that the linear regulator required for the contactless operation introduces a power dissipation even in the case of an operation with a power supply through physical contacts.
It would be desirable, in a dual-mode smart card, to allow switching from a contact operation to a contactless operation within a same communication session. Such a functionality is particularly advantageous in the case of smart cards coupled to portable devices provided with a battery. In such a case, the need to reset a communication session with the chip may impose an intervention of the user for a switching to a contactless operating mode. For example, in an application to mobile phones, an electronic chip of a smart card containing personal information of the user is by default in an operation with contacts with the rest of the mobile phone. This chip could be associated with a contactless operation, for example, to allow passing of automated public transport turnstiles by means of the same chip. Such an application cannot be envisaged with known systems, since this would force the user to cut a telephone communication to reset the smart card and then allow a selection to a contactless operating mode.